Empires for Roleplaying

When it comes to science-fiction roleplaying games, Traveller is granddaddy of them all, and it has it’s own setting (the Third Imperium) that’s been around from day one. Outside role-playing (but supported by several different games over the years) you have universes such as Star Wars, Star Trek and, more recently, The Expanse. But what other “universes” are there out there for adventuring, what kinds of stories might they inspire, and what RPG systems suit their particular style of story telling.